How do I get two way coupling in FLIP Fluids?
Well flip and manta dont support this.
However maybe you can fake it.
If you use a paint canvas for displacment you can mimic it a bit.
If the water moves wild your out of luck though.
There are some raindrops examples that might work.
Else you need some proffesional solver and an openvdb import
(if it supports that) to render it in Blender.
btw there's a popular youtube channel 2 minute papers has lots of research about this topic, maybe through that you can find software that does it.